Lactic bacteria are commonly used as ferments during the manufacture of certain food products, such as milk-based products (yogurts, cheeses, etc.), bakery products, wine, and meat-based products. In particular, these bacteria are used for their acidifying capacity. Indeed, lactic acid bacteria are capable of converting sugars (glucose, lactose, etc.) into lactic acid, or other acids, such as acetate, thereby provoking a decrease in pH.
Other types of bacteria are also commonly used as ferments; in particular bacteria which display nitrate reductase activity (NRA), such as certain bacteria of the Staphylococcus genus. These bacteria play an important role in the agri-food industry. In addition to their possible use for flavouring foods, these bacteria can be involved during nitrate-to-nitrite conversion processes, and more widely during a process for the manufacture of food products that includes such a step. Indeed, bacteria having NRA can be involved in the coloration of food products comprising myoglobin, irrespective of whether said products undergo a cooking step.
Thanks to the use of bacteria having NRA, in combination with nitrates that they will convert into nitrites (in situ nitrite production), it is possible to reduce the amount of nitrites used for the manufacture of food products such as cured products, or even to eliminate the introduction of chemical nitrites. Indeed, it is desirable to limit the amount of added nitrites since they can react with other compounds to form nitrosamines, which are known to be carcinogenic.
Bacterial combinations comprising lactic acid bacteria together with bacteria having NRA have also been developed and used as ferments during the manufacture of food products.
In the publication by M. Hugas and J. M. Monfort, entitled “Bacterial starter cultures for meat fermentation”, published in Food Chemistry, Volume 59, 4, pages 547-557, 1997, it is mentioned that, in the fermented sausage industry, the use of ferments consisting of a mixture of lactic acid bacteria strains with bacteria having nitrate reductase activity, is well established. Such bacterial mixtures are also disclosed in a book by J. Bacus, entitled “Utilization of microorganisms in meat processing, a handbook for meat plant operators”, published in 1984 by the publisher Research Studies Press Ltd.
However, such combinations are not always advantageous. For example, a publication by L H Stanke, entitled “Dried sausages fermented with Staphylococcus xylosus at different temperatures and with different ingredient levels”, published in 1995 in Meat Science, volume 41, No. 2, pages 179-191, discloses sausages incorporating Staphylococcus xylosus with various elements including the acidifying bacterium Pediococcus pentosaceus. Various temperatures are tested. The study reveals that the best temperature is 30° C. and the use of the lactic acid bacterium with Staphylococcus xylosus is not recommended, since the lactic acid bacteria appear to play an inhibitory role.
In the existing prior art combining both Staphylococcus and lactic acid bacteria, the lactic acid bacteria are used for their acidifying capacity and Staphylococcus strains are used for their NRA.